Keypad intensity on an electronic device may be adjusted for different operating environments. For example, in outdoor or sunlight conditions the keypad backlight may be turned off to conserve battery power. In normal indoor or office conditions, the keypad backlight may be turned off. In dim or dark conditions, the keypad backlight may be on to assist readability.
Mobile electronic handheld devices may include a light sensor for sampling ambient light conditions, on the basis of which display and/or keypad illumination or backlighting may be adjusted for readability in different operating environments (e.g. dimly lit environments, normal indoor environments and bright environments), for example as set forth in U.S. Pat. Nos. 6,961,044 and 7,352,930, and United States Patent Publication Nos. 20090109649, 20070097065, 20070002210 and 20050073446.
Improved Light Emitting Diode (LED) and light guide technology can result in keypad backlight intensity that approaches or exceeds display luminance in certain situations. The luminance of a display is dependent on its image content. Thus, a full white screen image may be bright and, as more dark pixels are added to the image, the screen image may appear to dim such that the keypad luminance exceeds display luminance. Keypad luminance in excess of display luminance can distract attention from the display, especially in dark ambient lighting conditions, which can make for less comfortable display viewing/reading.